 reserve R for 1-sorted;
 reserve X,Y for Subset of R;
 reserve R for finite 1-sorted;
 reserve X,Y for Subset of R;
 reserve R for finite Approximation_Space;
 reserve X,Y,Z,W for Subset of R;

theorem Prop3b:
  Y c= Z implies kappa_2 (X,Y) <= kappa_2 (X,Z)
  proof
    assume Y c= Z; then
    X` \/ Y c= X` \/ Z by XBOOLE_1:9;
    hence thesis by XREAL_1:72,NAT_1:43;
  end;
